FILE - In this March 24, 2014 file photo, Tiger Woods looks down during a news conference at the Newseum in Washington. Woods says his recovery from back surgery is going slowly and he's not sure when he'll be able to return to golf. In a wide-ranging blog on his website Monday, May 5, 2014, Woods says he remains sore from the incision during the March 31 operation for a pinched nerve. (AP Photo/Susan Walsh, File)

Robert Mueller’s special counsel investigation into Russian meddling in the 2016 election has cost $6.7 million during the first four and a half months of the probe. Click to see past independent counsel investigations guilty of racking up high bills.